Journal of Biomedical Physics & Engineering
Volume:2 Issue: 4, Jul-Aug 2012

The potential hazards of exposure to radiation from radon have been of great concern worldwide, as it is associated with an increased risk of lung cancer. Radon (222Rn) and its progeny are the main sources of radioactivity in the environment. The half-life of 222Rn (3.82 days) is long enough for it to diffuse into and build up in homes. 220Rn or thoron from the 232Th series, and 219Rn—a decay product of 235U—have very short half-lives (55.6 and 3.96 sec, respectively) and are of minor significance compared to 222Rn in the 238U series. However, these sources, like thoron, are important in uranium mines. Radon and thoron progeny decay by emitting β particles accompanied by γ radiation. Although γ rays are comparatively less damaging to the respiratory system than α and β particles, it is the principal deposited energy in other organs. Comparison of radon and thoron γ radiation dosimetry was performed using a modified Oak Ridge national laboratory (ORNL) adult mathematical phantom and the Monte Carlo N-particle transport code (MCNP). The results showed that the highest amount of the absorbed dose was in the lung followed by the thymus and heart, according to the ICRP103 publication. The absorbed dose from thoron was quite large in comparison to radon because thoron has more high-energy particles than radon.

Muscle fatigue is an important issue in neuromuscular rehabilitation. Better control of this phenomenon would result in better prevention of its consequent physiological damages. To provide a mathematical representation of muscle fatigue as a function of time. We conducted this study by combining the EMG-based estimation methods of muscle activation with the available muscle fitness equations describing the electrically evoked muscular contractions. Two groups of experiments were devised to produce a set of isometric and dynamic contractions in two hand muscles—biceps and deltoid—in a healthy man. The relevant surface EMG signals recorded simultaneously from the target muscles, provided the data needed for this process. Secondly, a number of EMG-based fatigue indices including peak to peak amplitude, root mean square values, average rectified values, number of zero crossings and mean frequency, were evaluated for the assessment of fatigue in the devised experiments. The mentioned indices were then, plotted as a function of the calculated fatigue, so that a mathematical representation of their relationship could be achieved. The results showed an overall increase in fatigue index for both groups of contractions as time passed, and, as was expected, the calculated fatigue in dynamic experiments stood at lower levels, having some fluctuations, in comparison to the isometric ones. The mathematical relationships between the time and frequencydomain fatigue indices and the proposed index were compatible with the previous experimental observations. These findings could be applied for the assessment and control of muscle fatigue in FES-research studies.

Pre-exposure to radiofrequency radiations of mobile phones would significantly increase the survival rate of exposed animals compared to those exposed to a lethal dose of gamma radiation alone. Stimulation of the immune system is believed to be a key mechanism for the induction of this phenomenon, the so-called “adaptive response.” The immune system protects organisms against infection with multiple lines of defense of increasing specificity. In this animal study, the effect of pre-exposure to radiofrequency on the survival adaptive response of a group of BALB/c mice which received intraperitoneal injections of Escherichia coli was investigated. Groups of BALB/c mice (exposure groups) were exposed to radiofrequency radiations emitted from a GSM mobile phone for 2, 4, 8 or 12 hours a day for 3 days. Other groups (sham exposed groups) were treated as exposure groups but the mobile phone was switched off during the experiment. On day 4, animals received intraperitoneal injections of E. coli. Survival of the animals was carefully monitored by an expert scientist. 15 days after exposure to the bacteria, the survival rate of the animals exposed to mobile radiations for 12 h/day was significantly (p=0.021) higher than those which only exposed to the bacteria (no pre-exposure to radiofrequency). Pre-exposure of BALB/c mice to radiofrequency radiations emitted from a GSM mobile phone increases their resistance to E. coli infection. This finding may have important clinical implications in treating bacterial infections

Many people suffer from nerve injury. The time consuming nature of the treatments makes the condition worse. Therefore, finding a way to accelerate the process of nerve repair is very important. To determine the effect of ultrasound on the acceleration of crushed peripheral nerve regeneration. The experimental model included crushed rat’s sciatic nerve. 40 rats were categorized into control and test groups. We used functional and electrophysiological tests to measure the amount of nerve regeneration. We extracted SFI from rats paw print for functional test and measured CMAP wave amplitude for electrophysiological test. After testing 3 types of ultrasound radiation parameters, we selected the best parameters. Ultrasound radiation in test group had the intensity of 0.2 W/cm2 and frequency of 3 MHz. It was applied 3 days per week for 2 min each time starting 72 h after the injury. Control group just received sham expose. During the treatment period, both SFI and CMAP amplitude was significantly higher in test group than in control groups (p<0.05). We found that ultrasound accelerates injured peripheral nerve regeneration. In addition, type of injury can be assessed according to changes in CMAP amplitude during the treatment period.

Changes in body composition may be used for monitoring progression/ regression of a disease. Prompt γ-rays in vivo neutron activation analysis (IVNAA) has been widely used for the measurement of body composition in recent years. In this paper, we tried to improve the safety of IVNAA operator. The most important factor for reducing the operator receiving dose is the optimization of shields. An appropriate shield should not only reduce the operator receiving dose, but it also must have the least effect on the detected spectrum. Because all parts of setup, including the operator shield, can be activated, the emitted γ-rays may be counted in detectors and increase the background level. In this research, several shields have been considered for an IVNAA setup. 4 different shields—concrete, epoxy colemanite resin, paraffin borated with bismuth layer (PE-Bi layer), and paraffin borated uniformly mixed with bismuth (PE-Bi)—were simulated by MCNPX code. We found that the PE-Bi shield decreases the absorbed dose to 77% compared with “no shield” and 74% compared to concrete. Also, the reduction rate of dose equivalent was 95% compared to “no shield” and 91% compared to colemanite resin. The neutron flux decreased almost 400 times in the presence of PE-Bi; it had less background in γ-spectrum compared to other suggested shields. Among the tested shields, PE-Bi would be the best one.